Printing head for matrix printer

ABSTRACT

A printing head for a dot-matrix printer having one or more annular arrays of radially mounted electromagnets driving print wires located closely adjacent to the center-line axis of the printed character, which axis also corresponds to the center of the annular arrays. The printing head also includes a collector plate having a single aperture for the print wires near the printing face, and means for supporting and driving the printing head. With this printing head mass is kept to a minimum, printing wires are radially disposed to the axis of the printed character and are geometrically closer thereto. This reduces energy losses associated with flexure and friction, and increases printing speed.

United States Patent 11 1 Matschke PRINTING HEAD FOR MATRIX PRINTER [75}lnventor: Arthur L. Matschke, Westport,

Conn.; Jack K. Horowitz, Laurelton, NY.

[73] Assignees: Tele Speed Communications, Inc.,

Syosett, N.Y.

[22] Filed: Oct. 17,1973

[2|] Appl, No; 407,236

521 U.S. c1. 197/1 R; 101 9105 51 11.1.0. B411 3/05 58 Field of Search197/1 R; 101 9305 2, l 29.065 3,2 I 7,640 3333,66"! 3,690,43l

Howard l97/l R Sept. 9, 1975 Attorney, Agent, or FirmJames J. Burke, ll

[57] ABSTRACT A printing head for a dot-matrix printer having one ormore annular arrays of radially mounted electromagnets driving printwires located closely adjacent to the center-line aitis of the printedcharacter, which axis also corresponds to the center of the annulararrays. The printing head also includes a collector plate having asingle aperture for the print wires near the print ing face, and meansfor supporting and driving the printing head. With this printing headmass is kept to a minimum, printing wires are radially disposed to theaxis of the printed character and are geometrically closer thereto. Thisreduces energy losses associated with flexure and friction, andincreases printing speed.

20 Claims, 4 Drawing Figures PATENTEDsEP' ems 3.904.011

saw 1 or 2 PRINTING HEAD FOR MATRIX PRINTER BACKGROUND OF THE INVENTIONThe present invention relates generally to dot-matrix printing and, moreparticularly, it relates to printing heads for dot-matrix printers.

A dot-matrix printer is one which forms an alphanumeric character from aplurality of dots by forcing the ends of selected printing wires from anarray of such wires into contact with a printing medium, i.e. an inkedribbon, and the recording medium or copy. In one arrangement, the arraycomprises seven wires in a vertical row which produces a character in afive pulse sequence, with horizontal movement of the array or recordingmedium between each pulse. Alternatively, the array may comprise 35wires arranged in five rows of seven wires each, which will produce acharacter with a single pulse, horizontal movement occurring onlybetween characters. As the character printed is of the usual size oftypewritten alphanumeric characters, about 0. l inch X 0. l inch, it isappreciated that the individual wires in a 7 X array must be of smalldiameter. The present invention is principally adapted for a 7 X 5 arrayof printing wires and will be described in connection with such anarray, but it could be adapted for other arrays as well.

The printing head of a dot-matrix printer will comprise l an array ofelectromagnets for converting electrical impulses into mechanical force,(2) printing wires driven by individual electromagnets, (3) meansguiding the printing wires into close proximity at the printing face,(4) suitable supporting structure, and, except in printers where theprinting head is stationary and the medium moves horizontally, (5)horizontal drive and return means. To facilitate quick printing headhorizontal movement, including starting, stopping, accurate positioningand quick return, it is desirable that the printing head have the leastmass possible.

Electromagnets of the type generally employed heretofore in this servicehave an axially moveable armature within a core carrying a winding, andthe print wire is secured to one end of the armature. Energizing theelectromagnets forces the wire against the printing medium and, at thesame time, the armature compresses or tensions a spring. The springprovides the force necessary to return the armature and wire to theirretracted positions when the coil is de-energized. One problem that hasarisen with such devices is the tendency of the print wire to work loosefrom the armature.

Perhaps the most serious problem in the design of a 7 X 5 dot-matrixprinting head results from the necessarily large space between adjacentwires at the electromagnet end thereof (due to the size of theelectromagnets) and the very close spacing therebetween at the printingface. This results in the printing wires l being of differing lengths,(2) traveling differing tortuous paths at differing angles to theprinting face, or (3) a combination of these two. While the mass of theprinting wire may be small compared to the mass of the armature,differing wire lengths can cause nonuniformity in printing unless thisis compensated for in some way. Flexing of wires during the printingstroke will require tubular guides or the like, and frictional lossescaused thereby reduce the force available for printing and also causenon-uniformity of printing and high rates of wear. A 35 electromagnetprinting head will necessarily have many electromagnets and associatedprint wires far removed from the centerline axis of the printedcharacter. This can be as much as 30, and means that substantial energymust be expended overcoming friction of the wire against a guiding tube.Compensation for this results in increasing the mass of the printinghead (through provision of more powerful electromagnets).

An array of electromagnets in close proximity to each other createsadditional problems. In a high speed printer producing 200 charactersper second, the electromagnets will generate a substantial amount ofheat. Special provision for cooling must be made since theelectromagnets are too closely spaced for natural convection to takecare of the load. The close spacing can also cause cross-talk problems,due to overlapping magnetic fields, which also impairs the quality ofprinting.

It would be desirable for dot-matrix printers to produce a solid ornear-solid appearing character, but this has not been possibleheretofore. The print wires, approaching the printing face from variousangles, are still slightly spaced at the printing face; the printedcharacter is thus a collection of discrete dots.

OBJECTS OF THE INVENTION It is a general object of the present inventionto provide an improved printing head for a dot-matrix printer.

Another object of the present invention is to provide a printing head oflow mass for dot-matrix printers.

A further object of the present invention is to provide a printing headfor dot-matrix printers which is capable of producing solid-appearingcharacters.

A still further object of the present invention is to provide a printinghead for dot-matrix printers wherein all print wires bend through an arcof large radius, and wire flexure is minimized.

Yet another object of the present invention is to provide a printinghead for a dot-matrix printer wherein cooling and cross-talk problemsare substantially avoided.

A still further object of the present invention is to provide a printinghead for a dot-matrix printer wherein all print wires are closelyadjacent the centerline axis of the printed character throughout theirentire length.

Another object of the present invention is to provide a printing headfor a dot-matrix printer that is simple, economical and reliable.

Various other objects and advantages of the present invention willbecome clear from the following detailed description of an embodimentthereof, and the novel features will be particularly pointed out inconnection with the appended claims.

THE DRAWINGS Reference will hereinafter be made to the accompanyingdrawings, wherein:

FIG. I is a side elevation view of a printing head in accordance withthe present invention, with all but four electromagnet units deleted forclarity of illustration;

FlG. 2 is a left end elevation view of the FIG. 1 embodiment;

FIG. 3 is a right end elevation view of the FIG. 1 embodiment, takenalong line 3--3 of FIG. 1; and

FIG. 4 is a detailed side elevation view of an electromagnetparticularly designed and adapted for use in the FIG. 1 embodiment.

DESCRIPTION OF EMBODIMENTS In essence, the present invention comprisesan array of specially designed electromagnets radially mounted on a pairof annular array plates around the centerline axis of the printedcharacter. Energizing of an electromagnet moves its spring-mountedarmature into contact with a pole piece thereof, and a print wire,connected to the armature by a right-angle shoe very close to saidcenterline axis, is moved into contact with the printing medium. Theprinting head also includes a transition bearing plate and a collectorbearing assembly at the printing face, but other wire-guiding means arenot required, because the print wires are very close to the centerlineaxis along their entire length, are all of substantially the same lengthand all bend through substantially the same large-radius arc. Supportmeans, electrical connection, drive means and ribbon guide means arealso provided.

The present invention differs from prior art dotmatrix printing headsprimarily in avoiding the moveable central armature type of solenoidwhich has the print wire attached at one end. Rather, there is provideda simple leaf spring armature having a shoe terminating in a right angleprint wire, which extends back across the axis of the magnet. Thisallows the electromagnets to be mounted in a circle around thecenterline axis of the printed character, with all said shoes very closethereto. While all of the electromagnets for a 7 X array could bemounted in a single circle, it would have to be of impractically largediameter, and it is preferred to mount them in two planes in circleshaving diameters which are not unduly large. Print wires attached toshoes in one plane are not precisely as long as print wires from theother, but this is not a serious problem.

At the printing face, all of the print wires are on or parallel to thecenterline axis of the printed character, and they pass through a singleaperture in sliding contact with each other and with the walls of theaperture. This contrasts with prior art printers, where printing wiresapproach the printing face at a slight angle through discrete apertures,and there is friction and wear between wire and aperture with eachstroke. By using a single aperture, substantially solid appearingcharacters are produced, and friction and wear are actually reduced.This is because wear occurs only along the line of contact between anenergized printing wire and one that is at rest and/or the wall of theaperture. On a given stroke there is no friction or wear betweenadjoining energized printing wires. Since there is only a few degrees ofcurvature in any print wire, it has a higher column strength and issubject to less flexure than wires in prior art printers. This increasesprinting efficiency and reduces wire wear.

By virtue of the radial mounting of the electromagnets in a pair ofplanes, there exists considerable spacing therebetween whichsubstantially eliminates cooling and cross-talk problems.

A preferred embodiment of the printing head of the present invention isillustrated in FIGS. 1-3, and attention is directed thereto.

The printing head 10 is mounted within the printer (not shown) on alower carriage bearing shaft 12 and an upper carriage bearing shaft 14.The printing head 10 is supported on a base including a pair of bearingsupport legs 16, 18 each having a horizontal bore 20 which accommodatesshaft 10. Legs l6, 18 are also provided with timing belt clamps 22 towhich the timing belt 24 is secured. Suitable means (not shown) areutilized to drive timing belt 24 and thus move printing head 10 alongshaft 12.

A print head base plate 26 is integral with the top surfaces of bearingsupport legs 16, 18, securing them in spaced relation on shaft 12. Baseplate 26 supports the printing mechanism. Specifically, at the forwardside (nearest the printing surface) of the printing head, base plate 26includes an upwardly extending carriage bean ing bridge 28, to which aresecured a wire bearing transition plate 30, a bridge element 32 and anadjustableaperture wire collector bearing plate 34, the structure andfunction of which are set forth in more detail hereinbelow. On the sideof the print head away from the printing surface, base plate 26 has anupwardly extending boss 36, which serves as a mounting block for theinner and outer electromagnet array plates 38, 40, also described below.It is preferred that legs l6, 18, plate 26 bearing bridge 28 and boss 36be formed as a single machined casting of a non-magnetic andheatdissipating material. Lastly, plate 26 also includes a bracket 42for mounting a photoswitch encoder 44. The later element co-acts with asequence encoder strip 46 mounted on the main chassis of the printer foruse in electromagnet pulse control. Bracket 42 is shown as a discretepart but could also be integral with plate 26.

Array plate 38, 40 can be merely flat and rectangular and have a large,round bore 48 therein, but minimum mass requirements make it preferableto have the upper portion 50 rounded. Functionally plates 38, 40 couldbe considered as a circular frame having a mounting leg on the lowerportion. it will be appreciated that other arrangements for mountingarray plates 38, 40 could be employed. Rigidity of plates 38, 40 will beimproved if a plurality of spacer bars (not shown) are employedtherebetween.

A plurality of electromagnets 52 are radially deployed at spacedintervals around the periphery of bore 48, on each of array plates 38,40, by a bracket 54 formed on one pole piece of the electromagnet.Electromagnets 52 can be considered as having a generally l-shaped corewith bracket 54 extending outwardly from the left side of the top, whereit is secured to the front surface of the array plate. Further, theinward surfaces of array plates 38, 40 are angularly milled, so that themounting surfaces of brackets 54 slope inwardly to form an acute anglewith the printing axis, rather than being normal thereto. The angle atwhich the brackets 54 (and electromagnets) are mounted determines thearc of the print wires, as hereafter discussed.

Outer array plate 40 has a bracket 56 secured along the top edge toprovide a mounting for stabilizer bearing 58 which rides on uppercarriage bearing shaft 14. This stabilizes the head and prevents anyrotation of the printing head around shaft 12.

Electromagnets 52 are described and claimed in U.S. Pat. No. 3,836,880issued Sept. 17, 1974 and assigned to the same assignee as the presentapplication. They are also shown in FIG. 4 and attention is directedthereto.

The electromagnet 52 comprises a core 60 with two integral pole sections62, 54, a spring 64 mounted with and adjacent to one pole section, afield shunt 66 and a shoe 67 attached to spring 64. A printing wire 68is attached to the free or distal end of shoe 67. Core 60 of coursecarries a winding 70, shown in part. Array plate 38 is also shown inpart.

Core 60 with pole sections 62, 54 must be made of a suitable magneticmaterial or magnetizable material, as must the field shunt 66. It ispreferred that core 60 and pole sections 62, 54 be formed as an integralunit, but this is not necessary. In the embodiment shown, core 60 has arounded rectangular cross-section. This is not a necessary feature, butprovides sufficient flux with minimum mass.

Pole section 54 is located at the outer end of core 60 and comprises aflat plate portion 72 of dimensions suitable to retain the cross-sectionof winding 70, and a leg 74 at one side, to provide a mountingstructure. Leg 74 has a machined surface 76 including a slot 77. Spring64 is secured between slot 77 and the angularly milled surface of arrayplate 38, a threaded hole 78 for receiving a screw (not shown) beingprovided for this purpose.

As shown in FIG. 4, surface 76 is generally but not necessarily parallelto the axis of core 60. The precise angle of surface 76 determined thegap and the printing stroke. The inner surface of plate portion 72 ispro vided with a step-shaped recess 80 adjacent surface 76 to receivethe free end of field shunt 66. This improves magnetic field continuityand provides a mechanical dampener for the moving spring, shunt and shoeassembly on the return stroke, when the free end of shunt 66 will abutrecess 80.

Spring 64 is a leaf spring made out of a suitable material such asspring steel or beryllium-copper, and extends down past inner polesection 62. The field shunt 66 and shoe 67 are secured to spring 64 atits free end by a pair of screws 82, 84. Shunt 66 is essentially a barof magnetic material extending from a point opposite inner pole section62 into recess 80 on the plate portion 72 of outer pole section 54. Soas not to impede the motion of spring 64, and to optimize massdistribution and inertial loads, field shunt 66 is undercut at 86, nearscrews 82, 84, a small distance. This permits free movement of spring64.

Inner pole section 62 includes a surface 88 forming a strike platespaced from and opposed to the secured end of field shunt 66. Surface 88is not quite parallel with the axis of core 60, but is rather angledslightly so as to be parallel with the opposing surface of field shunt66 when the electromagnet is energized, spring 64 ro tates in an arefrom surface 77, and the two surfaces are brought into contact. The gap90 between surface 88 and field shunt 66 is roughly one-half the desiredlength of stroke of each printing wire. The lower surface 92 of polesection 62 is configured to provide required flux strength and minimummass.

Shoe 67 is also secured to spring 64 by means of screws 82, 84, but onthe opposite side thereof to field shunt 66. Shoe 67 extends beyondsolenoid S2 to near the center of bore 48. It is important that shoe 67be rigid (i.e. not subject to flexure) and of sufiicient mass forprinting requirements. The print wire 68 is secured in the distal end ofshoe 67 and extends back across the axis of core 60 to the printingface.

Thus, when coil is energized, shunt piece 66 is drawn across gap andtoward strike plate 88, tensioning spring 64 and moving print wire 68the required distance into contact with the printing and recordingmedium (not shown).

In conventional solenoids, the armature moves away from the center ofthe flux field as the stroke proceeds. As a result, the greatest forceis generated at the beginning of a stroke. With the present invention,the force increases as gap 90 is reduced, and is greatest at the momentof impact with the printing medium. Again with a conventional solenoid,the armature must move the desired length of the printing stroke plusthe distance necessary to accomodate any flexure. With the presentinvention, the distance travelled by shunt 66 across gap 90 is only afraction of the distance travelled by print wires 68, because of thelarger radius through which the distal end of shoe 67 travels. Not onlydoes this allow a smaller gap 90 for a given length of printing stroke,but it also provides a higher angular velocity for print wires 68 thanfor shunt 66. These are all advantageous in dot-matrix printing.

it is preferred that print wires 68 be made of a wearresistant,low-friction material, and in this service electropolished tungsten wireis preferred. It will be appreciated from geometrical considerationsthat the less curvature there is in wires 68, the more printing energywill be delivered at the printing face and the less energy will bedissipated in flexure. It is preferred that such flexure as willinevitably occur take place near shoe 67 rather than where the wires arein close proximity to each other and to bearing plate 30. The lattercould cause momentary delays in wire movement and slow printing rate. Tothis end, the angle at which electromagnets 52 are mounted is such thatwires 68 travel through an arc of shorter radius adjacent shoe 67, whichradius increases with distance therefrom. Over all, wires 68 describe anapproximately parabolic arc with the short radius near shoe 67.

Print wires 68 extend from shoes 67 into the aperture 96 in collectorwire bearing plate 34 in the large radius are as described above. As anadditional aid in guiding print wires 68, transition wire bearing plate30 may be provided at an intermediate point. Transition plate 30 has 35discrete holes (not shown) for print wires 68, arranged in a patternthat is intermediate the doublecircle pattern of the wires in the planesarray plates 38, 40 and the 7 X 5 rectangular pattern at the face.Adjacent the printing face, the wires 68 are confined in a singleaperture 96 in collector wire bearing plate 34. Aperture 96 is nominally0.070 inch X 0. lOO inch, but adjustable, so as to accomodate differingsizes of print wires 68, as well as providing the ability to compensatefor wire wear.

As noted hereinabove, the use of a single aperture 96 to contain allprint wires 68 is a distinct advantage of the present invention. Notonly is wire wear reduced, but by framing the wires 68 in this way,squareness of the characters is insured, the distance between theprinting face and the recording medium is less critical, and clear,substantially solid-appearing characters are produced.

Bridge element 32 may also be provided with outwardly extending arms 98(FIG. 3) to act as supports for ribbon guides 100 (one shown).

In FIG. 1, certain ancillary printer features which are not part of thepresent invention are shown in phantom. These are paper guides 102 andfloating platen 104.

It will be appreciated that print wires 68 connected to electromagnets52 mounted on outer array plate 40 will necessarily be somewhat b ngerthan those mounted on inner array plate 38. The difference in masscaused by these two wire lengths is not sufficient to affect printingquality, but it is preferred that the inner mounting surfaces of the twoarray plates be machined at slightly different angles so that printwires 68 from the planes of both array plates have essentially the samegeometry and flexure characteristics.

If desired, logic circuity for driving the solenoids can be mounted onthe printing head 10. As shown in FIG. 1, the circuit board 106 issecured on suitable brackets to the underside of legs l6, 18. This maysimplify electrical connection (not shown) from the signal input toelectromagnets 52.

It should be apparent from the foregoing that the printing head of thepresent invention accomplishes the stated objects by providing a pair ofradial electromagnet arrays that enable all printing wires to be locatednear the centerline axis of printed characters. The radial electromagnetmounting also enables the electromagnets to be so spaced that coolingand cross-talk problems are essentially eliminated. The printing head ofthe invention is of low mass, but has a weight-topower ratio sufficientfor superior printing (in fact, it weighs no more than knownseven-solenoid printing heads The increased depth of printing field, dueto all print wires being parallel at the printing face, makes theprinter easier to use because platen adjustment is seldom required.Those skilled in the art will appreciate that in any successful printinghead the flux paths, pulse widths, mass, intertia, resonances, decayrates and overall geometry must be considered and carefully coordinatedin order to achieve optimum results of fast and trouble-free printing.

Various changes in the details, steps, materials and arrangement ofparts, which have herein been described and illustrated to explain thenature of the invention, may be made by those skilled in the art withinthe principle and scope of the invention as defined in the appendedclaims and their equivalents.

What is claimed is:

1. Printing head for dot-matrix printing at a printing face comprising:

means for supporting said printing head within a printer;

electromagnet mounting means on said support means spaced from theprinting face of said printer and including vertical plate means havinga large diameter bore therein;

printing wire collector plate means mounted on said support meansadjacent the printing face of said printer and having a single printingwire aperture therein; the axis of which defines the centerline axis ofa character to be printed;

a plurality of electromagnets mounted around the periphery of said boreand having armature means terminating in shoe means extending at theirdistal ends to near said centerline axis at a small angle to a planenormal to said axis:

each said electromagnet including a core having an axis extendingradially from said centerline axis;

energizing of said electromagnets functioning to move said distal end ofsaid shoe means toward said aperture a distance equal to a desiredprinting wire stroke; and

printing wire means extending from each said shoe means into saidaperture and terminating in a plane parallel and closely adjacent tosaid printing face, each said printing wire means describing an arc oflarge radius.

2. The printing head as claimed in claim 1, wherein said support meansincludes drive means for moving said printing head parallel to saidprinting face.

3. The printing head as claimed in claim 1, wherein said electromagnetmounting means includes a pair of said vertical plate means in spaced,parallel relation.

4. The printing head as claimed in claim 1, and additionally comprisingtransition plate means intermediate said shoe means and said collectorplate means including apertures guiding said printing wire means.

5. The printing head as claimed in claim 1, wherein the axis of saidbore is coincident with the centerline axis of characters to be printed.

6. The printing head as claimed in claim 1, wherein said are is anapproximately parabolic are having its shortest radius at said shoemeans.

7. The printing head as claimed in claim 1, wherein said electromagnetmeans include spring return means to retract said shoe means to a restposition when said electromagnet means is de-energized.

8. The printing head as'claimed in claim 1, wherein each said printingwire means extends from said shoe means back across the axis of the coreto its associated electromagnet.

9. The printing head as claimed in claim 7, wherein each saidelectromagnet comprises:

magnetic means including two opposed pole sections and a core extendingtherebetween;

a coil surrounding said core between said pole sections;

said armature means comprising:

leaf spring means secured to one said pole section and extendingsubstantially parallel to the axis of said core to the other said polesection;

magnetic field shunt means secured to said spring means and extendingbetween but spaced from said pole sections;

said shoe means secured to said spring means and extending therebeyond;and

said printing wire means extending back across the axis of said core.

10. The printing head as claimed in claim 1, and additionally comprisingcircuit means for selectively energizing said electromagnet means inaccordance with received signals.

1 l. The printing head as claimed in claim 1, wherein said printing wireaperture is adjustable.

12. The printing head as claimed in claim 3, including 35 of saidelectromagnets, said aperture retaining said printing wires in aseven-by-five array.

13. Printing head for dot-matrix printing at a printing face comprising:

means for supporting said printing head within a printer;

electromagnet mounting means on said support means spaced from theprinting face of said printer and including vertical plate meansparallel to said printing face and having a large diameter bore therein;

printing wire collector plate means mounted on said support meansadjacent said printing face and having a single, adjustable printingwire aperture therein, the axis of which defines the centerline axis ofcharacters to be printed;

plurality of electromagnets radially mounted around the periphery ofsaid bore, each said electromagnet comprising: magnetic means includingtwo opposed pole sections and a core extending therebetween, the axis ofsaid core extending radially from said centerline axis; a coilsurrounding said core between said pole sections', leaf spring meanssecured to one said pole section and extending substantially parallel tothe axis of said core to the other pole section; magnetic field shuntmeans secured to said spring means and extending between but normallyspaced from said pole sections; shoe means secured to said spring meansand extending at the distal end thereof to near said centerline axis ata small angle to a plane normal to said axis;

printing wire means extending from each said shoe means back across theaxis of said core and into said aperture, and terminating in a planeparallel and closely adjacent to said printing face, each said printingwire means describing an arc of large radius;

energizing of said electromagnets functioning to move the distal end ofsaid shoe means toward said aperture a distance equal to a desiredprinting wire stroke.

14. The printing head as claimed in claim 13, wherein said support meansincludes drive means for moving said printing head parallel to saidprinting face.

15. The printing head as claimed in claim 13, wherein said electromagnetmounting means includes a pair of said vertical plate means in spaced,parallel relation.

16. The printing head as claimed in claim 13, and additionallycomprising transition plate means intermediate said shoe means and saidcollector plate means including apertures guiding said printing wiremeans.

17. The printing head as claimed in claim 13, wherein the axis of saidbore is coincident with the centerline axis of characters to be printed.

18. The printing head as claimed in claim 13, wherein said arc is anapproximately parabolic arc having its shortest radius at said shoemeans.

19. The printing head as claimed in claim 13, and additionallycomprising circuit means for selectively energizing said electromagnetmeans in accordance with received signals.

20. The printing head as claimed in claim 15, including 35 of saidelectromagnets, said aperture retaining said printing wires in aseven-by-five array.

UNETED STA'IES PA'IU'NT OFFERS}:

CERI ICHTE OF CORRECLY.UN

Matschke, Arthur L. Horowitz, Jack K.

It is certified that error appears in the above-idontified patent andthat said Letters Patent are hereby corrected as shown below:

Column 8, line 32: "to" should be --of-.

Signzd and Scaled this eighteenth D ay Of November 1 9 75 [SEAL] AIIeSIZRUTH C. MASON MARSHALL DANN .-|11 '.\-rmg ()fju'er (umnusxmm'r u]lurvnrx and TruJvmur/u

1. Printing head for dot-matriX printing at a printing face comprising:means for supporting said printing head within a printer; electromagnetmounting means on said support means spaced from the printing face ofsaid printer and including vertical plate means having a large diameterbore therein; printing wire collector plate means mounted on saidsupport means adjacent the printing face of said printer and having asingle printing wire aperture therein; the axis of which defines thecenterline axis of a character to be printed; a plurality ofelectromagnets mounted around the periphery of said bore and havingarmature means terminating in shoe means extending at their distal endsto near said centerline axis at a small angle to a plane normal to saidaxis; each said electromagnet including a core having an axis extendingradially from said centerline axis; energizing of said electromagnetsfunctioning to move said distal end of said shoe means toward saidaperture a distance equal to a desired printing wire stroke; andprinting wire means extending from each said shoe means into saidaperture and terminating in a plane parallel and closely adjacent tosaid printing face, each said printing wire means describing an arc oflarge radius.
 2. The printing head as claimed in claim 1, wherein saidsupport means includes drive means for moving said printing headparallel to said printing face.
 3. The printing head as claimed in claim1, wherein said electromagnet mounting means includes a pair of saidvertical plate means in spaced, parallel relation.
 4. The printing headas claimed in claim 1, and additionally comprising transition platemeans intermediate said shoe means and said collector plate meansincluding apertures guiding said printing wire means.
 5. The printinghead as claimed in claim 1, wherein the axis of said bore is coincidentwith the centerline axis of characters to be printed.
 6. The printinghead as claimed in claim 1, wherein said arc is an approximatelyparabolic arc having its shortest radius at said shoe means.
 7. Theprinting head as claimed in claim 1, wherein said electromagnet meansinclude spring return means to retract said shoe means to a restposition when said electromagnet means is de-energized.
 8. The printinghead as claimed in claim 1, wherein each said printing wire meansextends from said shoe means back across the axis of the core to itsassociated electromagnet.
 9. The printing head as claimed in claim 7,wherein each said electromagnet comprises: magnetic means including twoopposed pole sections and a core extending therebetween; a coilsurrounding said core between said pole sections; said armature meanscomprising: leaf spring means secured to one said pole section andextending substantially parallel to the axis of said core to the othersaid pole section; magnetic field shunt means secured to said springmeans and extending between but spaced from said pole sections; saidshoe means secured to said spring means and extending therebeyond; andsaid printing wire means extending back across the axis of said core.10. The printing head as claimed in claim 1, and additionally comprisingcircuit means for selectively energizing said electromagnet means inaccordance with received signals.
 11. The printing head as claimed inclaim 1, wherein said printing wire aperture is adjustable.
 12. Theprinting head as claimed in claim 3, including 35 of saidelectromagnets, said aperture retaining said printing wires in aseven-by-five array.
 13. Printing head for dot-matrix printing at aprinting face comprising: means for supporting said printing head withina printer; electromagnet mounting means on said support means spacedfrom the printing face of said printer and including vertical platemeans parallel to said printing face and having a large diameter boretherein; printing wire collector plate means mounted on said supportmeaNs adjacent said printing face and having a single, adjustableprinting wire aperture therein, the axis of which defines the centerlineaxis of characters to be printed; a plurality of electromagnets radiallymounted around the periphery of said bore, each said electromagnetcomprising: magnetic means including two opposed pole sections and acore extending therebetween, the axis of said core extending radiallyfrom said centerline axis; a coil surrounding said core between saidpole sections; leaf spring means secured to one said pole section andextending substantially parallel to the axis of said core to the otherpole section; magnetic field shunt means secured to said spring meansand extending between but normally spaced from said pole sections; shoemeans secured to said spring means and extending at the distal endthereof to near said centerline axis at a small angle to a plane normalto said axis; printing wire means extending from each said shoe meansback across the axis of said core and into said aperture, andterminating in a plane parallel and closely adjacent to said printingface, each said printing wire means describing an arc of large radius;energizing of said electromagnets functioning to move the distal end ofsaid shoe means toward said aperture a distance equal to a desiredprinting wire stroke.
 14. The printing head as claimed in claim 13,wherein said support means includes drive means for moving said printinghead parallel to said printing face.
 15. The printing head as claimed inclaim 13, wherein said electromagnet mounting means includes a pair ofsaid vertical plate means in spaced, parallel relation.
 16. The printinghead as claimed in claim 13, and additionally comprising transitionplate means intermediate said shoe means and said collector plate meansincluding apertures guiding said printing wire means.
 17. The printinghead as claimed in claim 13, wherein the axis of said bore is coincidentwith the centerline axis of characters to be printed.
 18. The printinghead as claimed in claim 13, wherein said arc is an approximatelyparabolic arc having its shortest radius at said shoe means.
 19. Theprinting head as claimed in claim 13, and additionally comprisingcircuit means for selectively energizing said electromagnet means inaccordance with received signals.
 20. The printing head as claimed inclaim 15, including 35 of said electromagnets, said aperture retainingsaid printing wires in a seven-by-five array.